ADS Momentum simulation with varactor?
I am working on a filter design and I use ADS Momentum for simulation. Its a microstrip filter which is in a complex shape and can't be set up in ADS schematic. Now I want to add a varactor at some point to make it tunable but I don't know how to do it. So I guess I have to do this in schematic window to be able to sweep the biasing voltage of the varactor. I tried adding ports to the filter where I wanted to connect varactors then I created component, placed it in schematic, connected the varactors and biasing configuration and simulated but this ruined the output characteristics. Even without the varactors the output is not right due to extra ports. I think I don't have a clue what to do, this is the first time I am trying a do design a tunable filter.
The question is, how do I include varactors in a pure layout design Its not possible to add them directly into the design since they don't have layouts in ADS.
Thanks.
Before adding a varactor you can add just a capacitor and tune its capacitance in the range of Cmax and Cmin of the varactor.
See how filter behaves, and if you are happy just add the varactor and the DC bias.
The momentum don't support pure layout design. You must make component for the layout, and simulate it with capacitor in schematic.
As you know, the varactors are nonlinear capacitors and that's why they can be defined in a nonlinear equation with dependent coefficients.This is very simple to put in ADS schematic.. refer to user's guide
But first you should check your filter to be implemented with variable capacitors even they are linear.If your filter works properly then you can put these blackboxes with ploynomial definitions in your schematic.
But first of all, you must define those coefficients by either measuring or by using manufacturer's characterization data.
Thank you for all the answers. I tried with the capacitors and it seems to be working though it needs a lot of work. Will try nonlinear equations too. Cheers.